A network structure diagram of a Long Term Evolution Advanced (LTE-A) system is shown in FIG. 1, where an evolved Node B (eNB) is connected to a Core Net (CN) through wired interface, a Relay Node (RN) is connected to the eNB through wireless interface, and User Equipment (UE) is connected to the RN or the eNB through wireless interface.
Generally, there are two kinds of pilot signals in a Long Term Evolution (LTE) system (i.e., Release 8 generally mentioned), namely, a Reference Signal (RS) includes a Common Reference Signal (CRS) and a Dedicated Reference Signal (DRS).
The CRSs are sent by full band with specific configuration related to its Identity (ID) of one cell, that is, within one cell, modes of the CRSs are the same. A control channel, i.e., a Physical Downlink Control Channel (PDCCH) can only be demodulated by the CRSs, for the PDCCH is detected by several users simultaneously, and its pilot signal is supposed to be visible to all users and be identical.
The LTE-A system introduces a Demodulation Reference Signal (DM-RS) for user's data demodulation and a Channel State Information Reference Signal (CSI-RS) for UE reporting Channel Quality Indication (CQI)/Precoding Matrix Indicator (PMI)/Rank Indication (RI). Actually, DM-RS is very similar to dedicated user pilot signal of LTE system, and the difference mainly lies in that DM-RS supports the transmission of multi-data stream through multiple ports while dedicated user pilot signal of LTE system only supports the transmission of single-data stream through a single port. However, as time division duplex mode of RN needs to occupy OFDM (Orthogonal Frequency Division Multiplexing) symbol as transceiving handover time, which results in that the last OFDM symbol of backhaul subframe cannot be used. Therefore some proposals suggest using shifted DMRS patterns. However the CSI-RS generally refers to exclusive pilot signal of a cell. Presently, LTE-A has not yet determined pilot pattern of the CSI-RS which has two alternative schemes: Code Division Multiplexing across Time (CDMT) and Code Division Multiplexing across Frequency (CDMF), with specific positions for pilot signals being not determined either.
In relaying backhaul, as the last OFDM symbol of each subframe is to be used as transceiving handover time of the RN, it cannot be used in backhaul transmission. Therefore two revised DMRS transmission schemes have been proposed at present, namely, shifted DMRS pattern and punctured DMRS pattern, so as to prevent the DMRS from occupying in the last OFDM symbol. The four-port CRS and shifted DMRS pilot pattern in the related art are shown in FIG. 2, while the four-port CRS and punctured DMRS pilot pattern in the related art are shown in FIG. 3.
For In-band relay, the backhaul link shares band resource with an eNB-macro UE link, so its control channel R-PDCCH fails to conform to specifications of original R8 and needs to be modified. Currently, after the discussion of 3GPP RAN1 standard conference, the following conclusions have been reached for the design of R-PDCCH: an eNB is to send the R-PDCCH starting from the fourth symbol. Specifically a Downlink grant is sent within the first timeslot and an Uplink grant is sent within the second timeslot. Multiplexing modes for R-PDSCH, R-PDCCH, PDSCH and PDCCH are shown in FIG. 4.
In the course of implementing embodiments of the present invention, the inventors found out that there are at least the problems below in the related art:
In the current LTE-A system, there is no specific scheme for controlling resource allocation when the CSI-RS and the DM-RS exist in the R-PDCCH.